fix: on destroy remove the lastBootstrappedModule

If exit event was triggered twice we would try to destroy an already destroy module ref.

nativescript-angular/platform-common.ts

@@ -260,6 +260,8 @@ export class NativeScriptPlatformRef extends PlatformRef {
  "nativescript-angular/platform-common.exitCallback", () => {
  const lastModuleRef = lastBootstrappedModule ? lastBootstrappedModule.get() : null;
  if (lastModuleRef) {
+ lastBootstrappedModule = null;
+
  lastModuleRef.destroy();
  }